Report on Masaya (Nicaragua) — 24 February-1 March 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 24 February-1 March 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Masaya (Nicaragua). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 24 February-1 March 2016. Smithsonian Institution and US Geological Survey.
11.984°N, 86.161°W; summit elev. 635 m
All times are local (unless otherwise noted)
INETER reported that the lava lakes in three vents on the floor of Masaya's Santiago crater were active during 20 February-1 March. Volcanic tremor remained high and RSAM values were at high to very high levels. On 23 February small explosions ejected spatter onto the crater floor. During fieldwork volcanologists observed active lava lakes in all three vents on the crater floor, and noted that the inner walls of the crater were being eroded due to the lava lake. A new vent was forming on the SE part of the crater floor. During a second visit on 24 February INETER staff noted that the vents had become larger due to landslides on the crater walls. Small streams of lava sporadically originated from the NE vent. By 1 March the two vents in the SW part of the crater had almost merged.
Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.